Method of making piston-ring patterns



Mayv20, 1930. H. SEGRAVES 1 l(759,108

METHOD OF MAKING PISTON RING PATTERNS Filed Sept. 16. 1926 2Sheets-Sheet 1 gmnntoo May 20, 1930. H. s. GRAVES I METHOD of MAKINGPISTON RING PATTERNS Filed Sept. 16, 1926 2 Sheets-Sheet 2 Pym PatentedMay 20, 1930 UNITED STATES PATENT OFFICE HARRY S. GRA VES, OF DETROIT,MICHIGAN; ETHEL S. GRAVES ADMINISTRATRI X OF SAID HARRY S. GRAVES,DECEASED METHOD OF MAKING- PISTONRING PATTERNS Application filedSeptember 16, 1926. Serial No. 135,801.

In the manufacture of piston rings for internal combustion-engines,pumps and other apparatus wherein pistons are provided with variouskinds of packing rings, engageable with a cylinder wall, it is essentialthat such rings be round and have a predetermined force so as to exert apredetermined pressure against the wall of the cylinder for packingpurposes. In quantity production of the piston rings there are givendimensions and known qualifications to be incorporated in the castrings, so the preparation of patterns used for casting the rings is ofutmost importance. Obviously, if the pattern is not correct the ringwill not meet the specific re quirements, therefore the size and shapeof the pattern are very essential. In addition to this the'co-efiicientof expansion and contraction of a ring for a predetermined use is known,also the wall pressure expected from such ring, so in preparing apattern for a cast ring dimensions are used which will eventually resultin a ring of such size and configuration that it will exert a desiredwall pressure under predetermined operating'conditions.

This invention has special reference to the preparation of one or morepatterns for the production of cast piston rings, which will possess therequisite degree of resiliency. A pattern is prepared which is testedfor all requirements so that when a ring is cast it will possessinherent qualifications. This will expedite production of piston ringsin large quantities and insure a product that is as perfeet as can beobtained under quantity production. I

In the preparation of a piston ring pattern in accordance with thisinvention a method is involved which will now be described by aid of thedrawings, wherein V Figure 1 represents a print or chart of a pistonring of desired size;

Fig. 2 shows views of a ring made in accordance wit-h the print shown inFig. 1;

Fig. 3 shows a device for subjecting the ring of Fig. 2 to a forceequivalent to a redetermined wall pressure, so that the ring will beexpanded to approximately a configuration under such wall pressure;

Fig. 6 is a plan of a profile machine by which two or more masterpattern templets' may be produced;

F 7 is a cross sectional View of the same;

Flg. 8 shows views of a completed master pattern templet;

Fig. 9 shows views of a perfect master ring pattern;

Fig. 10 shows views of the master ring pattern supported by the masterpattern templet, and

Fig. 11 shows master pattern rings an ranged and held so that cast ringsmay be produced uniformly.

In the drawing, the reference numeral 1 denotes a chart, print orWorking drawing showing a plan in elevation of a split piston ring whichhas a width B, a thickness C, and an external diameter A. Fromthis-working drawing a split ring 2 is made having the dimensions A, Band C of the working drawmg.

The split ring 2 is placedon an expander or testing device 3, comprisinga stationary post 4, a scale 5, an adjustable anchorage 6 for one end ofthe scale, and a ring engaging member 7 at the opposite end of thescale.

The scale 5 may be of the graduated spring tension type and is adaptedto exert a pull on the ring 4 to expand the ring to a desired wallpressure, that is, to stress the ring to a configuration that it wouldassume if exerting a predetermined pressure against the wall of acylinder. The ring is placed on the device over the post 4' with thesplit or gap 8 a right angle to the minor axis which intersects thesplit or gap 8.

A master templet 9 is now prepared, as shown in Fig. A and the mastertemplet has a major axis 10 corresponding to the internal major axis ofthe expanded ring shown in Fig. 3. A minor axis 11 is also laid out onthe master templet corresponding to the internal minor axis of theexpanded ring and there may be other axes 12 corresponding to otherinternal axes of the expanded ring so that the periphery of the mastertemplet will be an exact reproduction of the inner periphery of theexpanded ring shown in Fig. 3. To test this master templet it may beplaced on the post 13 carried by the holder 14 of a conventional form ofmicrometer 15 and by rotating the master templet 9 the micrometer can beobserved to ascertain if the periphery of the master templet is correct.

Having produced such a master templet it is placed on the arbor 16 of aprofile machine shown in Figs. 6 and 7. The arbor 16 has a worm and geardrive 17 from a hand wheel 18 or any suitable source of power may beemployed for revolving the master templet equipped arbor. The profilemachine includes a carriage 19, preferably spring pressed so that aguide roller 20 of the carriage will at all times bear against themaster templet 9 mounted on one end of the arbor 16. On the opposite endof the arbor 16 are mounted two or more blank master pattern templets 21which in embryo form approach as near as possible the circumferentialconfiguration ot the master templet. One of these master patterntemplets is shown in Fig. 8 and it may be laid out with different axes22 with the major axis represented by w and the minor axis by 3 so thatthe quantity zr+y will represent the mean diameter.

However, with the embryo master pattern templets 21 on the arbor 16,these embryo templets may have the peripheries thereof brought intoengagement with the grinding wheel or instrumentality 23 which willproduce a periphery on the patterns corresponding to that of the mastertemplet 9, thus insuring accuracy in the reproduction of the masterpattern templets.

Having obtained master pattern templets, one of which may be used in onepart of a plant, while the other is used elsewhere, a perfectly roundmaster ring pattern 24 is made with an interior diameter approximate tothe quantity T This ring pattern is resilient enough to be placed overthe master pattern templet, as shown in Fig. 10 and if desired the sidewall of the ring pattern may be notched or provided with somedemarcation 25 which will indicate the location of the split or gap tobe eventually provided in the finished product. With the ring pattern24:

perfectly fitting the master pattern templet, which it must do, the ringpattern is now laid on a pattern board or support 26 and suitablysecured thereto, as at 27, so that it becomes an immovable patternfixture. After being attached to the board or support 26 the masterpattern templet 21 can be removed and used in stretching other ringpatterns for mounting on the board or support 26, as clearly shown inFig. 11, thus producing the gang or multiple ring pattern that may beused for easting a plurality of rings.

As a result of producing master patterns in accordance with this method,I have a ring pattern of a ring which has been subjected to allconditions and tested to meet the requirements of the cast ring on apiston in a cylinder. Rough dimensions have been obtained from theworking drawing and an embryo ring expanded for wall pressure. With thering under such predetermined pressure, dimensions, have been obtainedfor the preparation of a master templet and the templet has been used toproduce correspondingly shaped master pattern templets over whichperfectly formed rings may be stretched and held to such shape to beused as ring patterns for casting rings. After the rings are cast it isonly necessary to split or gap the same and this dimension having beenascertained from the embryo ring 2, under pressure as in Fig. 3, therequisite amount of ma terial can be removed from the cast rings, at theproper places, to permit of said rings contracting to perfect roundness.Since the embryo ring can be made of any desired dimension it is obviousthat allowance may be made for expansion and contraction, the embryoring being made oversize so that the master templet and master patterntemplet are actually oversize and thus take care of shrinkage due to thecooling of cast rings. In making these allowances and using the properamount of material in an embryo ring it is possible to produce a ring bycasting that will be perfectly round. It made oversize, the ring may bemounted on a mandrel and its periphery turned down to perfect sizewithout the metal being subjected to stresses and strains that wouldtend to produce a ring out-of-round.

In other words, there is a body of metal of such configuration as to beperfectly round when turned into a piston ring by my method.

What I claim is 1. A method of making a piston ring pattern, whichconsists in providing a split ring of the desired final circumferencesexpanding said split ring for wall pressure, making a master patterntemplet with dimensions corresponding to the expanded split ring,fitting a perfectly round ring over the master pattern templet, andfixing the pattern ring to hold its configuration when the masterpattern templet is removed.

2. A method of making a piston ring pattern, which method consists inproviding a templet, having a periphery approximating the internaldimensions'of a ring under Wall pressure condition, making a patternfrom said templet, fitting a ring over said pattern, and then fixing thering so that the pattern may be removed with the shape of the patternring maintained for molding purposes.

3. A method of making distorted piston ring patterns from a chart givingdimensions of a perfectly circular ring, said method consisting inmaking the ring according to said dimensions, expanding the ring toplace the same under tension corresponding to a desired Wall pressure,producing a templet having external dimensions corresponding to theinternal dimensions of the expanded ring, fitting a perfectly round ringpattern on said templet, and fixing said ring pattern so that thetemplet may be removed from the ring and used as a pattern in a mold.

4. A method of making a piston ring pattern consisting in providing atemplet pattern having a periphery approximating the internal dimensionsof a ring under Wall pressure conditions, fitting a ring over saidpattern, and then fixing the ring as fitted so that the pattern may beremoved With the shape of the ring maintained for molding purposes.

5. A method of making tensioned piston rings according to givendimensions, consisting in expanding a ring of such dimensions to placethe same under tension corresponding to a desired Wall pressure, andmaking a reproduction of said expanded ring.

6. A method of making tensioned piston rings according to givendimensions, consisting in expanding a ring of such dimensions to placethe same under tension corresponding 49 to a desired Wall pressure,producing a templet having external dimensions corresponding to theinternal dimensions of said expanded ring, producing a ring havinginternal dimensions equal to' the external dimensions of said templet,and reducing the last named ring to the dimensions of the first namedring.

In testimony whereof I aflix my signature.

HARRY s. GRAVES.

